If you’re a freelancer, chances are you need to track your time in order to bill your clients. And that can be a major hassle.

You might also be a mobile freelancer, like me, who uses multiple computers and wants to be able to work from anywhere. In that case, a web-based time tracker might be the way to go. You want something easy to use, cheap, with a nice interface. Preferably even fun to use.

Whatever your needs, here are 6 of the coolest tools for tracking your time. Most of them aren’t free, but then the best tools often aren’t.

1. Toggl. Nice interface, simple to use, and there’s both a web version and now a downloadable version (Windows only). And it’s free. Nuff said.

2. Tick. Very slick interface. A simple web-based interface, easy to use (after configuration), and fast. Pretty much all you’re looking for.

3. Harvest. One of the nicest interfaces around, Harvest is definitely a professional package. It works well for teams, it has project estimates, some great reports, and as a web app it’s available from anywhere. Like most of these apps, it has a pricing plan from free to premium.

4. Cashboard. The interface isn’t as slick as the first three on this list, but it does have some very useful and detailed features that go beyond tracking time, including producing and tracking invoices, keeping track of accounts and clients, producing estimates, and more.

5. FreshBooks. A slightly older-looking interface, when compared to the first few items on this list, but it’s a basic product that definitely gets the job done. If integrates with invoicing software which is useful when you’re billing by the hour.

6. yaTimer. The only app on this list that’s not available for the web, yaTimer is a downloadable desktop app. It’s also probably the simplest of the apps on this list, doing simple time tracking and not much else. For those with basic needs, it’s perfect.

Leo Babauta has been a reporter, editor, speech writer and freelance writer for the last 17 years. Leo writes for numerous blogs notably including LifeHack.org and his own blog about simple productivity, Zen Habits.net.